VIRULENCE OF ORGANISMS 5 



the power of inhibiting the bactericidal activity of the blood serum, 

 thus allowing the invader opportunity for further invasion. By- re- 

 peated injections of aggressin exudates into animals, Bail suc- 

 ceeded in immunizing these animals against various infections, thus 

 producing anti-aggressins. These rendered the bacteria defenseless 

 and permitted unhindered phagocytosis. The agglutinative power 

 of the sera of such animals was markedly enhanced. 



Wassermann and Citron, and many others, soon opposed Bail's 

 aggressin hypothesis, by pointing out that the phenomenon can be 

 explained without assuming that a new type of immune body is 

 concerned. Wassermann and Citron, Wolff, Sauerbeck, and also 

 Doerr found that the action of the so-called aggressins can be ex- 

 plained by the fact that exudates contain extracts of the bacteria. 

 Artificial aggressins were prepared by making extracts of bacteria 

 in vitro. It thus seems probable that the aggressins are nothing 

 more than endotoxins which have a negative chemotatic influence 

 and a non-specific action. Citron was able to show by means of com- 

 plement-fixation that the exudates contain free bacterial receptors, 

 which by absorbing immune bodies, tend to neutralize the destruc- 

 tive power of these antibodies. Levy and Fornet showed that fresh 

 twenty-four- to forty-eight-hour culture filtrates of bacillus 

 typhosus, paratyphosus, pyocyaneus and proteus possess non- 

 specific aggressive powers and, according to Ikomikoff, aggressins 

 of bacillus coli, staphylococci, and vibrios will act interchangeably, 

 thus showing the non-specific nature of these substances. From 

 Zinsser and Dwyer's experiments these bodies appear to be practi- 

 cally identical with anaphylatoxins (see page 218). The addition of ana- 

 phylatoxin to bacteria will change a sublethal dose into a lethal dose. 



Closely related to the aggressins are the " virulins " of Rosenow. 

 This author found that freshly isolated cultures of pneumococci 

 were not readily phagocyted, but this property was lost on repeated 

 subculture. He prepared salt solution extracts of the virulent 

 strains. Upon treating avirulent strains for twenty-four hours or 

 more with these extracts, the avirulent organisms became virulent 

 for animals, and at the same time resistant to phagocytosis. The 

 substance contained in the salt solution extracts capable of render- 

 ing the organisms virulent was named virulin. This substance ap- 

 pears to be essentially the same as the aggressin prepared in vitro 

 by Wassermann and Citron. In our opinion, these extracts, whether 

 prepared in the form of exudates or as extracts, contain poisonous 

 bodies which augment the invasiveness of the organism. They may 

 be non-specific bacterial proteins or protein products, such as are 

 probably contained in so-called anaphylatoxin. They may be 

 in part endotoxins. The anti-aggressins of Bail are agglutina- 

 tive and are probably called forth by the injection of the ex- 

 tracted bacterial proteins in the exudates or extracts. It seems 

 probable also that the effect of these anti-aggressins may depend 

 upon their agglutinative capacity. The subject is confused and in- 



